Trevor Mitchell, the principal rural fire officer for Hawke's Bay, said the overnight doubling of the fire was unexpected, but it was "still within containment area".
It was spreading northeast from Tangoio Settlement Rd and Mitchell said it was unlikely to be put out today.
Helicopters with monsoon buckets and at least 65 firefighters were battling eight fires around the Hawke's Bay region on Monday, including one in Waipatiki Forest that was burning out of control.
Mitchell said that fire had not crossed any roads overnight, with State Highway 2 still "miles away" from the flames.
He advised people to keep off Tangoio Settlement Rd, "unless you absolutely need to do business at Waipatiki".
He said the fire would likely be an issue for a few days until they got a perimeter around it.
Most firefighters withdrew from the fire on Monday by 6.30pm due to windy and dangerous conditions. By 9.30pm it had spread to 140ha and one house had been evacuated as a precaution.
Mitchell said the terrain and conditions meant that the forest fire was left to burn overnight.
Firefighters and aircraft could not fight the blaze in darkness, he said.
Winds have eased this morning but while isolated showers were forecast today, there would not be any steady rain.
Police asked motorists to avoid State Highway 50 as choking smoke covered the road.
